1. Niranjan Rao Julapelly Real-Time Scheduling [ Chapter 5.5]

2. Topics of Discussion Real-time Computing Synchronous Programming Languages Real-time Operating Systems Real-time System Types Real-time System Methodologies Real-time Scheduling Algorithms Real-time Scheduling Implementation Issues

3. Real –time Computing Software & hardware for systems which have real-time constraints and are interrupted often. Comprises of: Synchronous Programming Language. Real-time Operating System. Real-time Design Methodologies. Synchronous Programming Language Provides abstract modules for scheduling algorithms, parallelism, pre-emption. Finite state (execution time predictable), deterministic, synchronous dataflow. Declarative and Imperative Languages. Examples: Lustre, Quartz, SOL, Esterel.

4. Examples: Embedded Systems (Appliance Controller, Spacecraft, Robots, Industrial Control. “Control Program” – American Airlines, IBM – Later called “Sabre Airline Reservation System”. Real-Time Operating System (RTOS) Early Real-time Systems Recent Important Real-time Systems DSOS (Deep Six OS) – Geophysical Services Division, Texas Instruments. Ptolemy Project, University of California, Berkeley [8]. MARS (MAintainable Real-time System). ARTS Kernel. Spring Kernel. CHAOS Kernel. Alpha Kernel. Dragon Kernel.

5. Hard Real Time vs. Soft Real Time [McObject, 2006] Critical real-time systems such as nuclear power plants or fly-by-wire airplanes are Hard Real Time Non-critical real time systems where missed transactions only degrade system quality are Soft Real Time Firm real-time systems are similar to soft real-time, except late tasks are discarded. Scheduling algorithm depends on real time system characteristics

6. Hard deadline

7. Soft deadline

8. MASCOT (Modular Approach to Software Construction Operation and Test) - Architecture Oriented (RT Control & interface definition between concurrent processes) - British ground-air missile system. HOOD (Hierarchic Object-Oriented Design) - Hierarchical decomposition. - European Space Agency – Aerospace project. AADL (Architecture Analysis and Design Language) [6] - Automotive, aerospace industry. RTSJ (Real-Time Specification for Java) [7] Real-time System Design Methodologies

9. Real-time Scheduling Algorithms [Stankovic,’88] Classification Static vs Dynamic Preemptive vs Non-preemptive Global vs Local Examples Static: - Fixed-priority Rate-monotonic algorithm - Fixed-priority Deadline-monotonic algorithm - Graph based Approach Dynamic: - Earliest Deadline First - Least Laxity

10. Communication Delay - worst case execution time, non-deterministic RPC - Remote blocking Real-time Implementation issues in Distributed Systems [Kasavant, ‘88]

11. RT Research Groups RT computing lab: http://www.eecs.umich.edu/RTCL/ RT computation and communication group: http://www.cs.bu.edu/groups/realtime/ RT and embedded systems laboratory: http://www.cs.virginia.edu/~control/ Supercomputing and Parallel computing research group: http://www.cs.cmu.edu/~scandal/research-groups.html Systems Research group: http://www.cc.gatech.edu/systems/ Distributed systems research group: http://www-dsg.stanford.edu/ Institute for systems engineering, RT Systems group: http://www.rts.uni-hannover.de/index.php/Main_Page/index.htm Institute for computer engineering, RT Systems group: http://www.vmars.tuwien.ac.at/ IEEE Technical Committee on Real-Time Systems: http://cs-www.bu.edu/pub/ieee-rts/ Euromicro Technical Committee on Real-time Systems: http://www.ecrts.org RT Technical Commitees

12. RT Scientific conferences EventWebsite IEEE Real-time Technology and Applications Symposium, St. Louis, Missouri, USA - April 22-24, 2008 http://www.rtas.org/ ECRTS – Euromicro Conference on Real-time Systems http://www.ecrts.org/ IEEE Real-time Systems Symposium, Tuscon, Arizona, USA – Dec 3-6, 2007 http://www.rtss.org/ International Symposium on Object oriented Real-time Distributed systems http://ise.gmu.edu/isorc o7 IEEE International Conference on Embedded and Real-time Computing systems and Applications http://ssl.snu.ac.kr/~rt csa2007/

13. References 1.http://en.wikipedia.org/wiki/Real-time_operating_system 2.S. Cheng, J.A. Stankovic and K. Ramamritham, ‘‘Scheduling Algorithms for Hard Real-Time Systems: A Brief Survey’’, pp. 150-173 in Hard Real-Time Systems: Tutorial, IEEE (1988). 3.T. L. Casavant and J. G. Kuhl, ‘‘A Taxonomy of Scheduling in General Purpose Distributed Computing Systems’’, IEEE Transactions on Software Engineering 14(2), pp. 141-154 (February 1988). 4.A. Burns, ‘‘Scheduling Hard Real-Time Systems: A Review’’, Software Engineering Journal 6(3), pp. 116-128 (1991). 5.K. Ramamritham and J.A. Stankovic, ‘‘Dynamic Task Scheduling in Hard Real- Time Distributed Systems’’, IEEE Software 1(3), pp. 65-75 (July 1984). 6.McObject LLC, “Real-time Databases for Embedded Systems”, Precision Data Management, 2006